In solid-state image pickup units, to improve photoelectric conversion efficiency and sensitivity with respect to incident light, there has been proposed a so-called back-illuminated type structure in which a drive circuit is formed on a front surface of a semiconductor substrate and a back surface of the semiconductor substrate serves as a light reception surface. Moreover, there has been proposed a three-dimensional structure in which a circuit substrate where a drive circuit is formed is prepared in addition to a semiconductor substrate where a photoelectric conversion section is formed and the circuit substrate is bonded to a surface opposed to a light reception surface of the semiconductor substrate.
In such a back-illuminated type solid-state image pickup unit, a plurality of through hole vias reaching a drive circuit of a semiconductor substrate or a drive circuit of a circuit substrate are provided to a peripheral region located outside a pixel region including a photoelectric conversion section so as to penetrate the semiconductor substrate. A configuration on the light reception surface of the semiconductor is fabricated by the following processes. First, a cap film is provided on the light reception surface so as to cover the through hole vias that are so formed as to be embedded in the semiconductor substrate, and then a light-shielding film is provided on the cap film. Next, in the peripheral region provided with the through hole vias, a wiring line and an electrode pad allowing the through hole vias to be connected to one another are provided on the cap film. Then, a planarization film is provided so as to cover the wiring line and the electrode pad, and color filters and on-chip lenses corresponding to the respective photoelectric conversion sections are provided on the planarization film. Finally, in the peripheral region, the planarization film covering the wiring line and the electrode pad is selectively removed by etching to form a pad opening allowing the electrode pad to be exposed.
Moreover, a configuration on the light reception surface side of the back-illuminated type solid-state image pickup unit is as follows. A through hole via penetrating the semiconductor substrate is provided to a section peripheral to the pixel region where the photoelectric conversion sections are arrayed. The through hole via via is connected to a wiring line or a circuit substrate provided on a side opposed to the light reception surface. Moreover, a top on the light reception surface side is covered with an insulating film, and a pad wiring line such as a wiring line for connection or an electrode pad is provided on the insulating film. The pad wiring line is connected to the through hole via through a connection hole formed in the insulating film, and is connected to an external wiring line by wire bonding.
Further, an insulating film covering the pad wiring line is provided on the light reception surface side, and color filters and on-chip lenses corresponding to the respective photoelectric conversion sections are provided on the insulating film. Moreover, an opening allowing the pad wiring line to be exposed is provided to the insulating film covering the pad wiring line (refer to the following PTL 1 up to this point).